Latent image bar codes are exposed onto most currently produced 35 mm film. A DX bar code, in use for many years, is repetitively exposed at a fixed pitch corresponding to half frame intervals along one edge of the film and contains encoded information pertaining to what are referred to as product and gen (generation) codes that uniquely identify the film type and its production source. In the late 1980's, Fuji Photo Film, Ltd., introduced a film that incorporated a dedicated frame number bar code on the opposite edge of the film from the DX coded edge. This machine readable code allowed photofinishers to automatically determine frame numbers for each image frame that could then be printed on the processed photographic prints. At about the same time, an improved version of the DX code was developed by Eastman Kodak Company, assignee of the present invention, which, as disclosed in commonly assigned U.S. Pat. No. 4,965,628, embeds a frame number code within an extended version of the standard DX code. This new code is generally referred to as a DXN code. It has the advantage that, in addition to providing frame numbers for automatic printing of frame numbers on photoprints, it allows reading the frame number with existing bar code readers, thereby avoiding the need for a separate reader at the opposite edge of the film. Such an arrangement leaves the opposite edge of the film free for exposure of human readable information in alpha or alpha-numeric form.
It is known practice in commercially employed photoprinter equipment, such as represented by the CLAS35 high speed printer made and sold by Eastman Kodak Company, to assign frame numbers to image frame notch locations on a film order. The phrases "film order" and "film strip" are synonymous and are used interchangeably herein. The process employed is based on determining a frame number from the DXN code for one notch location on the film order and then using this as a reference position from which frame numbers can be calculated for the remaining notch locations on the order. The algorithm for this is as follows: ##EQU1## In this process, with reference to FIG. 2, when a bar coded frame number 35 is validly read, e.g. bar code 35a corresponding to half frame number 01A, the frame number and position of the bar code is captured. This becomes the reference bar code frame number. The frame number for each notch 16 is then determined by subtracting the position of the notch in question from the position of the reference bar code, dividing by the pitch 37 between adjacent bar codes and then adding (or subtracting) the resultant member, rounded to the nearest integer number, to the reference bar code frame number. The result is the assignment of the frame number (01) nearest to the notch 16a as the number for the corresponding image frame 17. Because, by convention, there are two alpha-numeric, half-frame numbers 40,41 for each full frame position, e.g. 22 and 22A, the processor, for algorithm purposes, assigns sequential decimal equivalent numbers to the half-frame numbers such that half-frame 22 becomes decimal frame number 44, half-frame 22A becomes decimal frame number 45, etc. Prior to actual printing of the frame numbers on resultant photographic prints, the decimal frame numbers are converted back to human readable alpha-numeric numbers. It will be appreciated from this description that this process is dependent on being able to read a frame number in the bar code to establish the reference bar code frame number.
The capability of automatically associating bar coded frame numbers with photoprints is a highly desirable feature offering for photofinishers. There remains, however, a substantial usage of DX coded film which does not allow this feature to be employed using existing bar code reader equipment. There is the possibility that an additional alpha numeric optical character reader may employed by the photoprinter, such as is disclosed in U.S. Pat. No. 4,823,163, to directly read the alpha numeric frame numbers that are also optically exposed at the edges of the film. The added cost and complexity of this added mechanism makes this approach very undesirable for the highly competitive and cost conscious photofinishing industry. Accordingly, there is a need for provision of the capability for existing photofinishing equipment employing bar code readers to perform automatic identification of image frame numbers on DX coded film so as to provide for automated printing of frame numbers on resulting photoprints.